This invention relates to a windmill apparatus, particularly to a sail-type windmill apparatus, which features a simplified structure with effective wind catching performance.
The known propeller-type windmills, through effective in utilization, are expensive in manufacturing cost and complex in structure. The anemometer-type windmills, though cheap for manufacturing, are ineffective in utilization. In addition, the structure of the known anemometer-type windmills usually includes a pair of hemespherical cups mounted in opposite direction on a vertical shaft. With the arrangement of the cups, when one of them is driven backward away from the wind, another one is moved forward against the wind so that, owing to the different wind pressure applied on the concave and the convex areas of the cups, the vertical shaft is rotated to drive a machine mechanically connected thereto through the turning of the cups. However, since the hemispherical cups incurs a good deal of resistance whenever they are moved forward against the wind, operational efficiency is therefore reduced.